Magnetic separator



P 1950 c. E. WUENSCH 2,522,556

MAGNETIC SEPARATOR Filed April 26, 1947 2 Sheets-Sheet 2 IN VEN TOR. CHARLES ERB WUE/VSCH A TI'OR/VEYS Patented Sept. 19, 1 950 MAGNETIC SEPARATOR Charles Erb Wuensch, San Francisco, Calif; by decree of distribution to Eunice L. Wuensch Application April 26, 1947, Serial No. 744,131

12 Claims. 1

This invention is concerned with the separation ,of finely divided magnetic, i. e. magnetizable material from a fluid in which it is suspended. More particularly, the invention relates to a wet magnetic separator for removing fine magnetizable particles from a slurry or slime or the like containing suspended non-magnetizable material, say finely divided gangue.

In sink and float processes and the like it has been proposed to employ finely divided magnetic material such, for example, as magnetite to increase the density of the medium in which the separation occurs. Such a medium, which in essence is a suspension of finely divided magnetic particles in liquid, say water, eventually becomes contaminated with non-magnetic slimes and must be purified. The separator of the instant invention, although of general utility in the separation of commin'uted magnetic material from a suspension in fluid (be it liquid or gaseous) is particularly adapted to the purification of heavy media of the character employed in sink and float processes, and is superior to conventional magnetic separators in that it has a higher capacity and utilizes its electromagnetic field more efficiently.

As indicated above, the apparatus of the invention is adapted primarily for the treatment of I slurries or the like in which all of the solid particles, both magnetic and non-magnetic, are of relatively small size, say all finer than 80 or 100 mesh. However, the apparatus is also adaptable to the treatment of slurries in which some of the non-magnetic solids are coarser than 80 or 100 mesh. In such case the non-magnetic coarse material will accompany the finer magnetic particles from the separator but may be removed subsequently by screening.

The apparatus of the invention, because of its relatively large capacity and the efficient use of its magnetic field, reduces capital and operating costs in the recovery and purification of magnetic material from suspension. It may be employed not only in ore concentration processes such as the well known sink and float operation but also the transportation of crushed ores in pipe lines, for example, in the process described in an article by me entitled Pipe Line Ore Transport May Lower Mining Costs appearing in the Engineering and Mining Journal for April 1944. The apparatus is also applicable in the removal of finely divided magnetic solids from oil well drilling muds and the like.

In essence, my invention contemplates the combination in a separator for removing fine magnetizable particles from suspension in a fluid which comprises a settling chamber, an inlet conduit for the suspension projecting downwardly into the chamber from the top, an outlet for separated fluid from the chamber disposed above the bottom of the inlet conduit, a magnet (preferably an electromagnet) so disposed with respect to the chamber that its lines of force pass through a space therein beside the inlet conduit'and below the outlet, 9. scraper for removing magnetizable particles attracted by the magnet to cause them to settle in the chamber below the space, a nonmagnetizable bafile disposed above the magnet and partially closing the space and another outlet for the magnetizable particles from the bottom of the chamber. Save for the magnet, the structure should be made of non-magnetizable material (say copper, brass, aluminum, wood, etc.) so as not to interfere with proper concentration of the magnetic field and resultant good operation.

In practice, a fluid suspension, say a mixture of gangue slimes and sand and finely divided magnetite in water, is introduced into the chamber through the inlet conduit. The fluid with the magnetizable and non-magnetizable material suspended therein seeks to rise through the adjacent relatively narrow space in the chamber to T the outlet. The magnetizable particles are attracted by the magnet and agglomerated within its field from which they are removed by the scraper. Thereupon they fall (or are carried) into the lower part of the chamber and are removed from the outlet. The non-magnetizable gangue and fine sand particles are carried up to and from the outlet by the rising current of fluid (say Water).

The non-magnetizable bailie disposed above the magnet prevents vagrant magnetizable particles from being carried out with the fluid. Preferably, it is disposed substantially within range of the lines of force to define an exit slot for the rising current in a zone where the magnetic field is not intense. If no baflle is employed, or if the baffle be magnetizable, some of the magnetizable particles tend to accumulate in the upper portion of the space or as a fringe at the overflow and to be carried out with the fluid.

My preferred separator employs a settling chamber of inverted conical shape. The magnet employed therein is annular in form and so disposed that its lines of force pass through the space in which the current of slurry rises from the inlet conduit. Thus the magnet may be in the form of two annular pole pieces spaced one above the other and separated by cores magnetized by means of coils wound around them.

In one form of the separator of my invention, the inlet conduit is centrally disposed in the upper portion of the settling chamber so that there is an annular space between it and the walls of the settling chamber in which the separation takes place. The annular magnet is disposed around the chamber beside this space and the magnetizable particles are attracted to the side of the chamber by the magnet. The battle takes the form of an annular ring turned inward- 1y adjacent the upper edge of the chamber above the magnet and a scraper mounted on a concentric rotatahle shaft removes the magnetizable material attracted by the magnet and causes it to drop toward the bottom of the cone. The shaft which carries the scrapers also carries on its lower portion a series of agitators or conveyors, say a set of interrupted screw flights which prevent the magnetizable solids from packing in the chamber and also aid the downward movement toward the outlet.

The magnetizable solids are removed from the lower portion of the chamber by pumping or the like. Preferably, the rate of withdrawal from the bottom of the chamber is governed by the density of the material settling in an intermediate part of the chamber. Thus, for example, a density gauge may be provided in the region of the agitators. This density gauge automatically controls a pump or a valve through which the magnetizable material is removed from the bottom of the cone. If the density of the material within the cone increases, the rate of withdrawal is increased automatically and vice versa. The device described and claimed in my co-pending application, Serial No. 579,117, filed February 21, 1945, is excellent for such control purposes. In order to most efficiently employ the magnetic field it may be desirable to dispose the entire magnet within the settling chamber, in which case it is desirable to alter the feeding mechanism as described hereinafter. These and other features of my invention will be understood more thoroughly in the light of the following detailed description taken in conjunction with the drawings of which:

Fig. 1 is a plan view of one form of magnetic separator of the invention;

Fig. 2 is a vertical sectional view through the apparatus of Fig. 1 taken along the line 2-2; and

Fig. 3 is a vertical sectional elevation of a modified form of the'separator of Figs. 1 and 2 in which the annular magnet is disposed entirely within the settling chamber.

The apparatus illustrated in Figs. 1 and 2, has a settling cone II) with conical walls which slope inwardly and down to an outlet portion I I. Feed is run into an inlet conduit or cone l2 of inverted frusto-conical shape disposed concentrically in the upper portion of the settling cone with its top above the upper rim of the cone. The apparatus is provided with a central vertical shaft l3 driven by a gear l4 and a worm [5 at its top and journaled at its bottom in an enclosed step bearing I6. In the portion of the cone below the inlet conduit the shaft is provided with an agitator I! in the form of a set of interrupted screw flights of progressively smaller diameter as the bottom is approached. The outer edges of these screw flights approach close to the wall of the settling cone.

There is a relatively narrow annular space between the inlet cone and the upper portion of the settling cone. A magnetic field is produced in this annular space by means of an electromagnet l9. This electromagnet comprises an upper annular pole. piece .20, a lower annular pole piece 2| and a series of cores 22A, 22B, 22C, 22D, 22E,

. 22F, 22G, 22H, which act as spacers and hold the two pole pieces apart. The annular magnet is of frusto-conical shape to conform to the wall of the cone. Thus its upper annular pole piece is of larger diameter than the lower. The annular magnet produces lines of force 23 (shown diagrammatically in Fig. 2) in the annular space within the upper portion of the settling chamber, the magnet being disposed adjacent this space onthe outside of the cone and concentric therewith. Immediately above the magnet there is an annular baflile 24 extending inwardly from the edge of the settling cone and partially closing the space in which magnetic separation occurs, leaving a narrow slot for outflow of fluid and non-magnetizable solids.

The shaft is provided witha pair of horizontal rigidly mounted arms 26,-21 provided respectively with scrapers 28, 29 on their outer rims. These scrapers move along the wall of the settling cone in the neighborhood of the magnet.

The settling cone is provided with an automatic density control which may be of any conventional form, preferably that described and claimed in my aforementioned co-pending application. Thus in Fig. 2 the density control device is shown as an upper diaphragm 30 in the wall of the cone in the region of the agitator and a lower diaphragm 3| disposed in the core below the upper diaphragm. Pressures registered by these diaphragms are transmitted to a gauge 32 which registers the differential density between the two diaphragms. As long as this differential density remains constant at a predetermined value a pump 33 attached to the lower outlet of the cone and controlled by the gauge operates at constant speed but as the difi'erential density increases the speed of the pump is automatically increased and vice versa. I

Any other convenient flow control on the outlet for the magnetizable material on the separator may be employed. For example, the gauge may be employed to control a valve instead of a pump.

An annular overflow launder is provided around the lip of the separating cone and this launder discharges into a second launder 35 that carries away the overflow from the apparatus.

In operating the apparatus of Figs. 1 and 2, feed, say a slurry of finely divided magnetite mesh or less), contaminated with gangue slimes is fed into the central inlet cone. The feed tends to rise and overflow from the lip of the cone due to a slight head established in the inlet cone. Thus there is a current of feed containing both magnetizable and non-magnetizable particles which rises as indicated in the annular space adjacent the magnet. The magnetizable particles are attracted by the magnet to the adjacent Wall of the settling cone. The rakes or scrapers (which are continuously rotated) tend to remove the agglomerated magnetized particles so that they settle into the lower portion of the 'cone. Non-magnetizable slimes and fine sand pass out with the water into the rim of the settling cone above the magnet, and the non-magnetizable baffle prevents the magnetic material from being washed over. The scrapers remove the magnetizable material before it can accumulate in quantities suflicient to pass the baflie.

The apparatus is operated continuously and the magnetizable particles are agitated in the lower part of the :cone and continuously withdrawn by the pump as hereinbefore described. If the feed contains coarse non-magnetizable particles having a high settling rate, these will settle along with the magnetizable material and be withdrawn from the bottom of the cone. However, a simple subsequent screening operation serves to separate these coarse particles from the magnetic material.

Naturally enough. the windings on the several magnet cores should be in the same direction so that the upper annular pole piece and the lower annular pole piece are uniformly opposed with respect to polarity.

In the apparatus of Figs. 1 and 2, the lines of force on the outside of the magnetic ring are not employed in separation. Improved eiflciency in this respect is offered by the apparatus of Fig. 3 wherein the magnet is within the settling chamber.

Referring to Fig. 3 it will be observed that it illustrates apparatus in general similar to that in Figs. 1 and 2, and comprising a settling cone 40 having a lower or outlet portion 4| and a pump 42 connected to the outlet portion for the withdrawal of settled material. The apparatus is provided with a central rotatable shaft 43 having an agitator 44 in the form of interrupted screw flights.

The upper portion of the apparatus is some what different, but as in the previous case there is a central frusto conical inlet 45 through which a portion of the feed enters. Another portion the feed enters the annular space 46 adjacent the upper rim of the cone, this space being defined on its inside by an annular frusto conical baflle or shield 41.

A magnet 48 is disposed in the upper portion of the settling cone between the two inlets for feed. As in the previous case it has an upper annular pole piece 49, a lower annular pole piece 50 and a series of wound cores of which two 52, 53 are shown. The magnet is hermetically sealed in a hollow ring 55 of nonmagnetizable material, say copper. This ring has an outwardly projecting upper bailie 58 and an inwardly pro ectmg baflie 51 in its upper portion.

The shaft is provided with a pair of rake arms 59, 60, both of which carry a pair of rakes numbered respectively 59A, 59B, 60A, 60B.

The operation of the apparatus of Fig. 3 is in general the same as that of Figs. 1 and 2, except that feed is supplied simultaneously through the inner cone and the outer channel 46. The feed tends to rise in the annular space in which the maget is disposed. The magnet attracts magnetizable material both toward its inside face and its outside face and this magnetizable material is raked out of the magnetic field by the dual rakes already described. The magnetizable material thus is caused to drop into the lower portion of the settling cone from whence it is removed as in the previous case.

Naturally enough, the apparatus of Fig. 3 can be provided with the automatic spigot control already described with reference to Fig. 2.

The slurry from which the magnetizable material has been removed in the apparatus of Fig. 3 is removed through a discharge pipe 62 passing through the side of the settling cone above th baflies at the top of the magnet.

At the outset it was indicated that the apparatus of the invention has a high capacity in terms of the space it occupies. This is in part due to the employment of an annular magnet.

of upwardly passing a thin rapidly rising stream of pul through the strong wide magnetic fleld provided by the apparatus with its lines of force transverse to the streamminimizes the trapping of non-magnetic material and consequently leads.

to cleaner separation. This is because the pull of the magnetic field on the magnetic material sets up cross-currents which operate with the rising current to bring about a cleansing action.

The agitators and scrapers re-agitate the magnetic pulp while conveying it downward and this also tends to free it of entrained non-magnetic particles.

It will be observed that the annular baflie above the magnet together with the adjacent slot are such that the rising current is i'ocussed at the slot a short distance away from upper pole piece, say 2 or 3 inches. The lines of force in the region of the slot are more dispersed than at the pole piece proper, and this aids in avoiding the trapp ng oi non-magnetic material. In other words, a classification of magnetic from nonmagnetic material takes place immediately below the baflle, the magnetic material moving into the region of greatest flux density, with the non-magnetic material being drawn in the opposite direction toward the draulic force.

Lastly, the annular baflle above the magnet tends to prevent magnetic material dislodged by the rake from being carried out the overflow zone of highest hyslot, after being built up as a fringe above the Thus for example, an annular magnet with a a baflle. By virtue of the baflle, magneticmaterial would have to move horizontally, against the magnetic field, in order to escape. So the baiile cooperates with the rake to permit continuous operation without loss of agglomerated magnetite, etc.

The agitating means in the lower portion of the apparatus may be a continuous spiral instead of the inter upted screw flights described above.

I claim:

1. In a separator for removing flne magnetizable particles from suspension in a fluid, the

combination which comprises a settling cham- 1 her, an inlet conduit for the suspension projecting downwardly into the chamber from the top, an outlet for separated fluid from the chamber above the bottom of the inlet conduit, an annular magnet disposed approximately concentri-.

cally with the upright axis of the chamber above the bottom of the inlet and below the outlet with its lines of force passing through the space in the upper portion of the chamber above the bottom of the inlet conduit and below the outlet, a scraper rotatably mounted in the chamber and having blades projecting into the space for removing magnetizable particles attracted by the magnet and causingthem to settle in the chamber, means for rotating the scraper, an annular non-magnetizable baiile disposed above the magnet and partially closing the space, and

another outlet for the settled magnetizable particles from the bottom'of the chamber.

2. In a separator for removing flne magnetizable particles from suspension in a fluid, the combination of which comprises a settling chamber, an inlet conduit for the suspension projecting downwardly into the chamber from the top, an overflow for separated fluid extending along the upper edge of the chamber above the bottom of the inlet conduit, an annular magnet disposed approximately concentrically with the upright axis of the chamber above the bottom tweenthe inlet conduit and the wall of the cham- Y ber below the overflow, a scraper rotatable in the chamber and having blades projecting into the space on the axis of the magnet for removing magnetizable particles attracted by the magnet and causing them to settle in the chamber, means for rotating the scraper, an annular non-magnetizable baflie disposed above the magnet and partially closing the annular space, and an outlet for the settled magnetizable particles from the bottom of the chamber.

3. In a separator for removing fine magnetizable particles from suspension in a fluid, the combination which comprises a settling chamher, an inlet conduit for the suspension projecting downwardly into the chamber from. the top, an outlet for separated fluid from the chamber above the bottom of the inlet conduit, a magnet disposed concentrically with respect to the chamber axis so that its lines of force pass through a space therein beside the inlet conduit and below the outlet, a scraper disposed adjacent the magnet for removing magnetizable particles attracted by the magnet and causing them to settle in the chamber below the space, means for moving the scraper, a non-magnetizable baille disposed above the magnet and partially closing the space, and another outlet for the settled magnetizable particles from the bottom of the chamber.

4. Apparatus according to claim 3 provided with agitating means disposed in the chamber below the inlet conduit.

5. Apparatus accordin to claim 3 in which the walls of the chamber slope inwardly toward the outlet for the settled magnetizable particles.

6. In a separator for removing fine magnetizable particles from suspension in a fluid, the combination which comprises a settling chamber, an inlet conduit for the suspension projecting downwardly into the chamber from the top and forming an annular space between the chamber wall and the inlet above the bottom of the inlet, an outlet for separated fluid from the chamber above the bottom of the inlet conduit, an annular magnet disposed approximately concentrically with the upright axis of the chamber with its lines of force passing through the annular space, a scraper rotatably mounted in the chamber on the axis of the magnet and having blades scraping against the portion of the wall of the chamber defining said space for removing magnetizable particles attracted by the magnet and causing them to settle in the chamber, an annular non-magnetizable baflie disposed above the magnet and partially closing the annular space, means for rotatin the scraper agitating means in the chamber below said space, and an outlet for the settled magnetizable particles from the bottom of the chamber.

'7. Apparatus according to claim 6 provided with a common shaft upon which the scraper and the agitating means are mounted.

8. Apparatus according to claim 6 in which the magnet is mounted in said space within the the magnet is mounted in said space within the chamber leaving passages both inside and outside the magnet for the movement of fluid, with scrapers provided in both passages and with bailles above the scrapers in both passages.

11. In a separator for removing fine magnetizable particles from suspension in a fluid, the combination which comprises a settling cham-. ber, a central conduit for the suspension projecting downwardly into the chamber from the top, an annular frusto-conical baflle disposed between the central conduit and the chamber and forming with the chamber an annular inlet conduit in the chamber around the upper edge thereof, leaving an annular space in the chamber between the two inlet conduits, an outlet conduit for separated fluid from n upper portion of said space, an annular magnet disposed approximately concentrically in the annular space between the central conduit and the annular baflle below the outlet conduit, scrapers rotatable in the chamber on the axis of the magnet having blades disposed in the annular space between the central conduit and the annular baflie for removing magnetizable particles attracted by the magnet and on, both the inside face of the annular baflle and outside face of the central conduit causing them to settle in the chamber, an annular non-magnetizable baflie disposed above the magnet and projecting beyond its inside and outside faces closing the annular space, means for rotating the scrapers and an outlet for the settled magnetizable particles from the bottom of the chamber.

12. In a separator for removing fine magnetizable particles from suspension in a fluid, the combination which comprises a settling chamber, an inlet conduit for the suspension projecting downwardly into the chamber from the top, an outlet conduit for separated fluid from the chamber above the bottom of the inlet conduit, an annular magnet disposed above the bottom of the inlet approximately concentrically with the upright axis of the chamber with its lines of force passing through a space in the chamber beside the inlet conduit, the magnet comprising annular pole pieces spaced one above the other with a plurality of cores therebetween, a scrapper in the space for removing magnetizable particles attracted by the magnet and causing them to settle in the chamber, means for moving the scraper, an annular, non-magnetizable. baflle disposed above the magnet and partially closing the space, and another outlet conduit for the settled magnetizable particles from the bottom of the chamber.

CHARLES ERB WUENSCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 602,720 Bowne Apr. 19, 1898 1,392,413 Gow Oct. 4, 1921 1,665,081 Andrews Apr. 3, 1928 1,768,550 Fekete July 1, 1930 2,373,635 Wuensch Apr. 10, 1945 FOREIGN PATENTS Number Country Date 4 14,644 Great Britain 1912 

